I recently had to get a SMOG test for my 86' 22R PU. It barely failed CO, by 0.08, from the maximum allowed. Everything else was within normal limits if not below. I don't use this PU that much, it's my HomeDepot beater. The last oil change was 6 months ago. I've already replaced the air filter and the plugs and wires are about 6 months old.
Can just doing an oil change get me below the maximum CO level?
"Rastamon" wrote in news:00098c64$0$2373$ snipped-for-privacy@news.astraweb.com:
No, an oil change wont help. CO is produced by incomplete oxidation of the hydrocarbons in the fuel mixture. If the oxidation was complete there would only be CO2 in the exhaust. So to reduce CO levels, you might want to tune the engine up. Did you tune it when you changed the plugs and wires? The new air filter might help a little if the old one was limiting air flow; you might try leaving it out for the test if you can get away with that.
The catalytic converter also lowers CO levels by transforming CO to CO2, but catalytic converters aren't cheap.
High CO means it is running too rich. Did the old plugs look carbon fouled? Many things can cause it to run rich. Is it running too cool, is the carburator choke sticking closed? Those are the first things to eliminate. Good luck. Al
I changed the oil and air filter, and it passed. Though I'm curious why the NO went up almost to the max.
State Emission Standards:
15 MPH - HC (PPM): 146 Max / 43 Ave CO(%): 1.04 Max / 0.16 Ave NO (PPM): 1136 Max / 406 Ave 25 MPH - HC (PPM): 118 Max / 32 Ave CO(%): 1.32 Max / 0.15 Ave NO (PPM): 1222 Max / 349 AveHere are the results before and after:
BEFORE:
15 MPH - HC (PPM): 72 CO(%): 1.20 NO (PPM): 259 25 MPH - HC (PPM): 78 CO(%): 1.24 NO (PPM): 285AFTER:
15 MPH - HC (PPM): 87 CO(%): 0.38 NO (PPM): 1130
The air filter must have been filthy causing a rich mixture and high CO. High NO means the EGR system is not functioning correctly. Good luck. Al
More likely the oil was diluted with gasoline and/or breaking down. Half the vehicles that have a marginal fail would pass if the owner was smart enough to change the oil before taking it in.
Nox can fail one day and pass the next if temperatures change (drop) 5 degrees or so. Can pass one day and fail the next if temps go up. The testing station is supposed to run a big fan pointed at the car when it's hot out. Failure to do so can cause a lot of false fails.
It was cool the day I ran the first test, about mid 80s. Then I got an oil change and a week later, it was more than 90F and there was a fire near by. Like I said, I don't use this truck much unless I have a HomeDepot run. One guy told me a lot of RV motorhomes fail because they still for long periods and don't get oil changes. I guess I'll change the oil, more often, even though it's not that dark.
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